Classification, Contract Prices, and Quantities for Each Contract

The high cost of work done by the wheel scrapers, as given in the above tables, is caused by the scrapers being used to a great extent for serving the elevating graders in excavating and filling runways, ditching pits, and cleaning mud from in front of the traction engines after showers. Some of the expense above was charged to the graders, but as the scrapers and graders were worked together in the same pits it was impracticable to keep an accurate account of the work done by each. Therefore, if the work done by both methods was considered in one total cost, the result would be more accurate.

The high cost of work done by elevating graders between Stations 145-163, where the canal was excavated to grade by these machines, was caused by the large quantity of hardpan, the high lift and the long haul; and between 163-196, on account of the hard material. On this section the use of graders was abandoned when within about 5 feet of grade, because the material became so hard that it could not be handled profitably with these machines, and the drag-bucket excavator and steam shovel were used to finish it.

The high cost of material removed by the steam shovel as stated

in above tables, is attributed to the soft condition of the bottom of cut, and the height to which material had to be raised over a track which could not be kept to surface and alignment on account of the soft condition of the spoil banks.

The wheel scrapers, elevating graders and steam shovel having removed the cream of the excavation in most instances, the dragbucket excavators were left the hard material which was mostly found near the bottom, besides being required to lift the material to a greater height. Another advantage of the drag-bucket ex

cavators over the wheel scrapers, elevating graders and steam shovel, was their ability to work successfully in pits containing from 2 to 3 feet of water, and the fact that ordinary rains did not interfere with their output. It was also the only machine on which two and three shifts were worked profitably.

Taking all the foregoing facts into consideration, it will be readily seen that the drag-bucket excavators were the most economical and satisfactory machines used in the excavation of Colbert Shoals Canal.

Only three laborers were required at shovel, as the shovel was idle part of the time on account of an insufficient number of cars being furnished.

ELEMENTS AFFECTING LOCK CONSTRUCTION ON CANALIZED RIVERS HAVING FIXED DAMS

BY

Mr. J. S. WALKER
Assistant Engineer

The location of locks for canalized rivers has not received suf ficient attention in the writings of American engineers. So far as known to the writer, the discussion on Mr. R. C. McCalla's paper on Improvement of the Black Warrior, Warrior, and Tombigbee Rivers in Alabama," published in the Transactions of the American Society of Civil Engineers, Volume XLIV, 1901, and chapter 1, part 3, of "The Improvement of Rivers," by B. F. Thomas and D. A. Watt, published in 1903, and occasional brief statements in the reports of the Chief of Engineers, U. S. Army, constitute the bulk of what has been written by American engineers on this subject.

During the years 1892 and 1896 locations were made for seventeen locks with fixed dams on the Cumberland River. At eight of these sites the locks have been built and seven have been placed in operation. Unless otherwise stated, this paper is a statement of the writer's individual experience and opinion gained on this work, and is intended to apply to such streams as the Cumberland River, and, by reason of its similar regimen, to the Tennessee above Chattanooga.

Experience has abundantly taught in Europe and America that the first essential in the location of locks on canalized rivers is that the elevations of the upper miter sill of the lower lock and the lower miter sill of the lock immediately above should be practically the same, and placed at a predetermined distance below the greatest draft to be provided for, and that the intervening pool should be assumed to be level, the slope of the canalized river being disregarded. A clearance of at least a foot should be found at the shallowest places in a pool over the navigable depth proposed. If the navigation is to be greatest at extreme low water, it